I've an 84 f150 with a 300. Duraspark 2,, EFI manifolds, and offy intake with a Holley 390. I just put the card and exhuast on recently.

The problem is that I have a rough idle. Even with the one barrel this truck seemed to do this. You can hear it missing at the exhuast, but you can also watch the motor shake slighty.

When you get on the gas it seems fine, it's only at idle. Warm idles at 1100 rpm, and when I put in in drive (auto tranny), it will drop to 500 or so and sometime actually quit.

It has signs of a vacuum leak, but I checked and checked, and connot find any. I have new plugs wire, cap and rotor button.

Could I have the carb set to lean?

Thanks

 

Lean carb is possible...

Timing...?

I have an unheated Clifford that idles rough on cold starts...'Been meaning to provide heat to it but haven't HAD too yet.

I also bumped up the jets on my 390 for the colder Winter air. The Holley instructions say "1 jet size larger for each 35 degree drop in temperature."

Broncr

 

It turned out to be a lean carb. I put a vaccum gauge on it and reset it the idle mixture. Seems to be running good now. *crosses fingers*